DE69827885T2 - Method for generating a multimodulation frame and associated modulator - Google Patents

Description

OBJECT OF THE INVENTION

The The present invention relates to a method of production a multi-modulation frame, as well as a modulator and a demodulator for the realization of the method. The modulator and the demodulator according to the present Invention can realized, for example, in a unit of a radio communication system be as in the attached claims announced.

A frame is defined as a signal comprising successive time intervals. Regarding 1 a multimodule frame is characterized in that it has at least two time intervals 1 and 2 each of which is defined by their respective modulation, which differ from each other.

STATE OF THE ART

One Frame of the type defined above can be used, for example, in the DECT (Digital Enhanced Cordless Telecommunications) standard, from the ETSI (European Telecommunications Standards Institute) is issued to the destination, the traffic capacity of at least one channel or Increase time interval, without the for other channels change defined modulation while keeping the compatibility to other units of the same system that do not have the Function to change have the modulation, to maintain.

With reference to the 1 . 2A and 2 B becomes, for example, a first time interval 1 defined by a GFSK (Gaussian Frequency Shift Keying) modulation already used in the DECT standard and a second time interval 2 is defined by a π / 4DQPSK (π / 4-differential quadrature phase shift keying) modulation. The two modulations define corresponding constellations that exist in the 2A and 2 B with reference to predefined reference axes.

in the DECT standard is the modulated signal through a spectral mask limited, wherein the modulated signal contained in this mask have to be.

If in the same frame two modulations are used, for example the modulations, which are in the 2A , respectively. 2 B On the one hand, with no control over the change from one modulation to the other, the resulting signal may on the one hand produce a spectrum that is not within the limited spectral mask and, on the other hand, contain intersymbol interference causing the loss of symbols coincident with the time Modulation changes coincide.

In POKLEMBA, J J: "Digital tracking loops for a programmable digital modern ", MILITARY COMMUNICATIONS CONFERENCE, 1992, MILCOM '92, CONFERENCE RECORD, COMMUNICATIONS - FUSING COMMAND, CONTROL AND INTELLIGENCE, IEEE SAN DIEGO, CA, USA, 11.-14. October 1992, NEW YORK, NY, USA, PAGE 644-650 I, a modulator is disclosed that is suitable for use with several Modulation method can be programmed and three caster loops contains so that a frame that according to different Modulations is modulated, demodulated. The frame corresponds however, not a DECT frame, and as a result, the frame becomes not according to GFSK and π / 4DQPSK methods modulated.

Out MORINAGA N ET AL: "INTELLIGENT RADIO COMMUNICATION TECHNIQUES FOR ADVANCED WIRELESS COMMUNICATIONS SYSTEMS ", IEICE TRANSACTIONS ON COMMUNICATIONS, INSTITUTE OF ELECTRONICS INFORMATION AND COMM. CLOSELY. TOKYO, JP, BAND E79-B, No. 3, pp. 214-221 an adaptive modulation technique known in which the modulation method from several different modulations based on the Traffic and the received signal level, d. H. C / Ic (power ratio of desired Signal to co-channel interference) selected becomes.

This Contains document but nothing about the change of modulation.

CHARACTERIZATION OF INVENTION

A The first object of the present invention is the provision a method for generating a multi-modulation frame, the defines a spectrum contained in an amplitude-limited spectral mask is and intersymbol interference suppressed.

One second object of the invention is the definition of a modulator, for the realization of the method defined by this invention.

consequently is a method for generating a multi-modulation frame, the at least a first time interval and a second time interval contains wherein the first and the second time interval by first, and second Modulations are defined, characterized in that the method includes a step-by-step transition that takes at least two steps has the coefficients of a modulation filter of one first set of coefficients, which is associated with the first modulation is to switch to a second set of coefficients, which associated with the second modulation.

typically, becomes the stage for the step-by-step exchange of coefficients successive partial changes the coefficients are realized, with some coefficients in each step in the first set of coefficients, the first modulation method are assigned to be changed into coefficients in the second sentence, which are associated with the second modulation method.

To the Example is the first modulation a GFSK modulation, and the second modulation is a π / 4DQPSK modulation.

One Modulator for implementing the method according to the invention contains modulation filter means and Means to the gradual change the coefficients of the modulation filter means from the first set of filter coefficients, which are associated with the first modulation, in the second sentence of Filter coefficients associated with the second modulation, to effect.

BRIEF DESCRIPTION OF THE FIGURES

A more detailed explanation of the present invention, as well as other features and advantages can be found in the following description based on the attached Figures in which:

1 shows a format of a multi-modulation frame;

The 2A and 2 B two constellations for GFSK, resp.

π / 4DQPSK modulation demonstrate;

3 shows a block diagram of a modulator according to the invention;

4 shows a block diagram of a demodulator according to the invention; and

5 in detail and in the form of a block diagram in the modulator of 3 contained filter shows.

DESCRIPTION OF THE INVENTION

The method according to the invention avoids the transient effects caused by the change of the modulation, such as intersymbol interference or phase jumps, which appear in each of the consecutive frames when the change of modulation without adjustment mechanism at the time, with reference to FIG on 1 the two time intervals 1 and 2 be separated is applied.

Regarding 3 For example, a modulator according to a first implementation of the invention includes a first multiplier 10 , a delay line 11 , a second multiplier 12 , an oversampler 13 , a configurable filter 14 and a digital / analog converter 15 , The binary signal bn is applied to a first input of the multiplier 10 applied, whose output signal on the one hand via the delay line 11 to a second input of the multiplier 10 and on the other hand to an input of the multiplier 12 is created. This multiplier 12 receives the signal e ^{j (π / M) n} via a second input, where n is a bit rank. The output of the multiplier 12 is about the oversampler 13 to an input of the configurable filter 14 connected. The output of the configurable filter 14 is to an input of the digital / analog converter 15 connected.

This modulator, as in 3 is suitable for carrying out both the GMSK modulation and the π / 4DQPSK modulation, wherein the GMSK modulation is equal to the GFSK modulation, if the following conditions are met:
B × T = 0.5; and
0.35 <h <0.70,
where B is the signal bandwidth, T is the duration of a symbol, and h is the value of the modulation index.

• – Für GMSK-Modulation: *bn ∈ {1, –1}; M = 2 und das konfigurierbare Filter 14 ist ein Gauß-Filter; und
• – Für π/4DQPSK-Modulation: *bn ∈ {1, j, –j, –1}; M = 4 und das konfigurierbare Filter 14 ist ein Root-Raised-Cosine-Filter;

The modulator off 3 Also suitable for performing both GMSK modulation and π / 4DQPSK modulation under the following conditions:

• - For GMSK modulation: * bn ∈ {1, -1}; M = 2 and the configurable filter 14 is a Gaussian filter; and
• - For π / 4DQPSK modulation: * bn ∈ {1, j, -j, -1}; M = 4 and the configurable filter 14 is a root raised cosine filter;

The for the Gaussian filters used in GMSK modulation performs intentionally Inter-symbol interference between the transient symbols.

There would be no special unknown problems resulting from this processing of the signal with GMSK modulation if this GMSK modulation with its associated Gaussian filter is not simultaneously in the same frame with a π / 4DQPSK modulation (or any other) and its associated root raised cosine filter (or the signal shaping filter corresponding to the modulation in question) would occur. In the case of a multimodule frame, the final symbols generate in field with GMSK modulation 1 ( 1 ) "Foothills", which are in the front symbols of field 2 extend with π / 4DQPSK modulation. This effect generates perturbations that lead to a systematic loss of symbols, which are at the time of transition between the two modulations GMSK and π / 4DQPSK. In order to overcome this problem, according to the invention, a method for generating a multi-modulation frame containing at least a first time interval 1 contains, which is defined by a first modulation and a second time interval 2 , which is defined by a second modulation, a step to step change with at least two steps, the coefficients of the configurable modulation filter 14 from a first set of coefficients associated with the GMSK modulation to a second set of coefficients associated with the π / 4DQPSK modulation.

The table on the next page shows a more detailed illustration of an example of a step to stepwise change the coefficients of the configurable modulation filter 14 ,

at Gaussian filters and Root-raised cosine filters used for GMSK or π / 4DQPSK modulation if the same number of coefficients are used, for example twelve (12) in the described implementation. This number of coefficients corresponds to the largest number, that of each filter type, Gaussian filter and root raised cosine filters. The following will be in shown in this table:

table

Table Legend

• Coefficients of the Gaussian filter (GMSK modulation)
• Coefficients of the root raised cosine filter
• Rank of adjusted bits with corresponding coefficients

• – Wenn das Symbol mit dem Rang (N – 2) der GMSK-Modulation eintrifft, sind alle Koeffizienten des konfigurierbaren Filters Koeffizienten des Gauß-Filters,
• – Wenn das Symbol mit dem Rang (N – 1) der GMSK-Modulation eintrifft, sind alle Koeffizienten des konfigurierbaren Filters Koeffizienten des Gauß-Filters, mit Ausnahme der ersten beiden Koeffizienten h(0) und h(1), die Koeffizienten des π/4DQPSK-Filters sind (Root-Raised-Cosine-Filter),
• – Wenn das letzte Symbol der GMSK-Modulation mit dem Rang (N) eintrifft, sind alle Koeffizienten des konfigurierbaren Filters Koeffizienten des Gauß-Filters, mit Ausnahme der ersten vier Koeffizienten h(0), h(1), h(2) und h(3), die Koeffizienten des π/4DQPSK-Filters sind,
• – Wenn das erste Symbol der π/4DQPSK-Modulation mit dem Rang (N + 1) eintrifft, sind die letzten sechs Koeffizienten des konfigurierbaren Filters Koeffizienten des Gauß-Filters und die ersten sechs sind Koeffizienten des π/4DQPSK-Filters,
• – und so weiter.

N denotes the rank of the last symbol with GMSK modulation

• - If the symbol arrives with the rank (N - 2) of the GMSK modulation, all coefficients of the configurable filter are coefficients of the Gaussian filter,
• - If the symbol arrives with the rank (N - 1) of the GMSK modulation, all coefficients of the configurable filter are coefficients of the Gaussian filter, with the exception of the first two coefficients h (0) and h (1), the coefficients of π / 4DQPSK filters are (Root-raised cosine filters),
• When the last symbol of GMSK modulation arrives at rank (N), all coefficients of the configurable filter are coefficients of the Gaussian filter, except for the first four coefficients h (0), h (1), h (2) and h (3), which are coefficients of the π / 4DQPSK filter,
• When the first symbol of the π / 4DQPSK modulation arrives at rank (N + 1), the last six coefficients of the configurable filter are coefficients of the Gaussian filter and the first six are coefficients of the π / 4DQPSK filter,
• - and so on.

Consequently will be the gradual change the coefficients by successive partial changes the coefficients are realized, with some coefficients in each step of the first set of coefficients, that of the first modulation is assigned to coefficients of the second set of coefficients changed which is associated with the second modulation.

Similarly, a step-by-step replacement stage may be used for the coefficients of the configurable modulation filter 14 of coefficients associated with π / 4DQPSK modulation are constructed in coefficients associated with GMSK modulation, with the transition from π / 4DQPSK modulation to GMSK modulation taking place. However, this stage does not seem to have the same importance because the problem arises when using the Gaussian filter for GMSK modulation which generates "tailwords" which interfere with the symbols of π / 4DQPSK modulation.

Regarding 5 Contains the configurable filter 14 a modulation filter 140 , a synchronization circuit 141 and a programming circuit 142 , The synchronization circuit 141 receives the bit stream bn and defines frame synchronization depending on predefined bits, for example synchronization bits in the received frame, and consequently the timing of the modulation change may be known. When the arrival of the bit of the rank (N - 2) of the frame is expected (see the table above), the synchronization circuit activates 141 the programming circuit 142 , which gradually increases the coefficients COEF of the modulation filter 140 loads as shown in the table above.

A demodulator for demodulating a multimodule frame generated by a modulator, described with reference to 3 has been described is in 4 shown.

The demodulator includes a root raised cosine filter 20 , a subsampler 21 and a first multiplier 22 which are connected in series. The first multiplier 22 receives the signal e ^{-j (π / M) n} via another input. The output of the first multiplier 22 can be connected to two branches that are displayed in parallel. A first branch is used to generate a differential output signal and includes a second multiplier 24 , a delay line 23 and a threshold detector 25 , The second multiplier 24 receives at a first input the output of first multiplier 22 and at a second input the same output signal from the first multiplier 22 that over the delay line 23 is delayed. The output signal of the second multiplier 24 is applied to an input of a threshold detector 25 created.

A second branch is used to generate a coherent output signal and includes a threshold detector 26 and a decoder 27 which are connected in series.

Although this description of the use of the demodulator is done with a fixed predefined demodulation filter (Root-raised cosine filter 20 ), a person skilled in the art can use two filters which are adapted to the shape of the received signal with GMSK or π / 4DQPSK modulation. In this case, the demodulator may include a step change step to change the coefficients of the demodulation filter from a first set of coefficients associated with the GMSK modulation to a second set of coefficients associated with the π / 4DQPSK modulation This is done according to the change of coefficients in the modulator as described above. The demodulator includes a configurable demodulation filter and circuitry for stepping the coefficients of this demodulation filter from a first set of coefficients matched to the first modulation waveform to a second set of coefficients adapted to the second modulation waveform is, and this is done according to the change of coefficients in the modulator. This modulator must also include a frame synchronization circuit to detect the time of the modulation change and then activate the coefficient exchange circuit.

Claims (7)

Method for generating a multimodulation frame that has at least a first time interval ( 1 ) and a second time interval ( 2 ), wherein the first and second time intervals ( 1 . 2 ) are defined by first and second modulations, respectively, characterized in that the method comprises a step for step change with at least two steps in order to obtain the coefficients of a modulation filter ( 140 ) from a first set of coefficients associated with the first modulation to switch to a second set of coefficients associated with the second modulation. Method according to claim 1, characterized in that the step for gradually changing of coefficients by means of successive partial changes the coefficient is realized, with some in each step Coefficients of the first set of coefficients, the first Modulation are assigned in coefficients of the second sentence be changed, which are assigned to the second modulation. Method according to claim 1, characterized in that the first modulation is a GFSK modulation and the second modulation a π / 4DQPSK modulation is. Modulator containing means adapted to implement the method according to claim 1, characterized in that it comprises modulation filter means ( 140 ) and means ( 141 . 142 ) for stepwise changing the coefficients of the modulation filter means ( 140 ) from a first set of filter coefficients associated with the first modulation to a second set of filter coefficients associated with the second modulation. Demodulator containing means that are adapted in that it receives a frame received from a modulator according to claim 4 demodulate, characterized in that it is a configurable Demodulation filter and stepwise change means the coefficients of the demodulation filter from a first set of coefficients, which is the waveform of the first modulation is adapted to a second set of coefficients, which the waveform of the second modulation is adapted, contains, and this according to the change the coefficient is performed in the modulator. Radio communication system containing mobile terminals, the a modulator according to claim 4 included. Radio communication system containing mobile terminals, the a demodulator according to claim 5 included.